MIJ-NSR Vol. 10, Art. 1, S.M. Widstrand et al.

Core-Level Photoemission From Stoichiometric GaN(0001)-1x1

S.M. Widstrand, K.O. Magnusson, L.S.O. Johansson, E. Moons, M. Gurnett
Karlstad University, Materials Physics, Universitetsgatan 2, 651 88 Karlstad, Sweden

M. Oshima
University of Tokyo, Department of Applied Chemistry, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

This article was received on Monday, December 13, 2004 and accepted on Friday, January 14, 2005.

Abstract

We report on a high-resolution x-ray photoelectron spectroscopy (HRXPS) study using synchrotron radiation, for the identification of the core level binding energies of Ga 3d and N 1s, from a stoichiometric Ga-polar GaN(0001)-1x1 sample.

Three surface shifted components were found on the stoichiometric surface for the Ga 3d feature. The first surface shifted component has a higher binding energy of 0.85 eV, and is interpreted as surface Ga with one of the N bonds replaced by an empty dangling bond. This structure is belonging to the stoichiometric clean and ordered Ga-polar GaN(0001)-1x1 surface. The second, with a binding energy relative the bulk of -0.76 eV, is interpreted as Ga with one of the bonds to a Ga atom, which indicates a slight excess of Ga on the surface. The third surface shifted component is shifted by 2.01 eV and is related to gallium oxide in different configurations.

The N 1s feature is complex with five surface shifted components relative the bulk were found. Two components with binding energy shifts of -0.54 eV and 0.47 eV are interpreted as surface shifted core levels from the stoichiometric, clean Ga-polar GaN(0001)-1x1 surface.

We also analysed the Ga 3d spectrum after deposition of 1.5 ML of Ga on a stoichiometric surface. The surface shift for the Ga 3d_5/2component from the Ga overlayer is -1.74 eV relative the bulk GaN.

The C 1s and O 1s core levels from remaining surface contamination have also been line shaped analysed and show complex structures.